This invention relates to mouthguards and in particular to a new and improved mouthguard adapted to minimize shock to the teeth and head area.
In the many contact sports played throughout the world, the use of mouthguards is nearly universal. Over the years many attempts have been made to develop a mouthguard that would offer suitable protection to the teeth and supporting structures. A number of surveys and studies have been conducted to evaluate the effectiveness of the various types of mouthguards. The results of these studies can be summarized broadly by the statement that any of the mouthguards will reduce oral injuries. A consensus seems to exist that all offer some type and degree of protection, however, the consensus also seems to be that the ideal mouthguard has not yet been developed.
In a recent study of Texas high school football athletes ("An Evaluation of Mouthguard Programs in Texas High School Football," by Richard R. Seals, Jr., DDS, et al, JADA, Vol. 110, p. 904, June 1985) more than 50% of the 534 reported injuries were concussions. The 269 concussions reported by 126 of the schools would tend to indicate a need to reevaluate the protection provided by mouthguards for concussions and other central nervous system injuries.
Most conventional mouthguards consist simply of U-shaped, trough-like members of resilient material, such as rubber or a suitable plastic, shaped to fit over the upper or lower teeth or both. While the typical mouthguard offers some protection for the teeth, such mouthguards provide little, if any, protection against head and neck injuries.
Normally, the head of the condyle of the mandible articulates with a cartilagenous disk or movable cartilogenous pad in the temporomandibular joint. It is this pad which glides between the condylar head of the mandible and the articular surface of the glenoid fossa of the temporal bone. When wearing conventional mouthguards, the athlete is subject to damage resulting from direct transmittal of force through the mandible, the thin layer of cartilage, and into the temporal bone and the cranial cavity. Substantial increases in intracranial pressure and cranial bone deformation have been shown to occur when a football player, for example, receives a blow on the chin or on the faceguard of the protective helmet. This results in a measurable deformation of the skull. Similar damage occurs in other contact sports, such as boxing, hockey, lacrosse, etc. Because of the use of protective helmets with faceguards for intercepting horizontal blows, the principal injuries to football players in the head area results from upward blows to the lower jaw, especially the chin area, and from upward blows to the faceguard which transmits force to the jaw through the chin strap.
In an attempt to solve this problem, U.S. Pat. No. 4,337,765 to E. S. Zimmerman discloses a mouthguard constructed so as to provide an increased separation between the mandible and the glenoid fossa, and to slightly increase this separation in the case of a blow to the chin or face. The Zimmerman mouthguard provides a pivoting action about a fulcrum point in the molar area to cause a slight rocking shock absorption motion. The Zimmerman premise is that in the case of a blow to the chin or face a pivoting action would occur about the lower first molar causing a slightly increased separation between the condyle of the mandible and the temporal bone. This is accomplished, supposedly, by placing a greater thickness of material in the bottom wall of the mouthguard in the region engaging the lower first molar. The difficulty of such a design is in achieving a balanced occlusion. Maintaining an increased separation in the first molar area would preclude teeth anterior and posterior to that point contacting firmly. Although Zimmerman states that the occlusion is balanced from first bicuspid to second molar while following the typical Curve of Spee, if such a state were achieved, it would preclude a static increased thickness in the area of the lower first molar. One either achieves a pivoting thickness or a balanced bite, but not both. In supposing a pivoting thickness was maintained in the Zimmerman mouthguard, we must look closer at what is achieved by such a design under function. Similar to all mouthguards or orthopedic repositioning appliances, the temporomandibular joint is placed in a rest state by simply opening the bite in a range of 3 to 5 millimeters. Such openings advance the head of the condyle anteriorly and inferiorly. This has been a long established premise in the treatment of temporomandibular joint disorders with occusally balanced hard acrylic orthopedic splints. Such a situation allows derangements and imbalances of the muscles and ligaments of the temporomandibular joint area to regain their tone and balance. Bringing about such a balance relieves patients suffering from a wide range of symptoms, often caused by an imbalanced occlusion. Use of the Zimmerman mouthguard by an athlete with a temporomandibular joint disorder may be hazardous. Further separation or opening of the temporomandibular joint and the rocking shock absorption technique upon receiving a blow to the lower jaw may only serve to place additional stresses on already imbalanced and symptomatic muscles and ligaments. This may result in tears and/or rips in the muscles and ligaments.